It is known that in many technical applications there is the need of orienting and placing tubular articles in a predetermined position to make them ready for a subsequent working operation. This problem is of special concern particularly in the stocking factories, as the stocking fabric is very thin and flexible and, accordingly, is unable to give the stockings a shape of their own. This occurs, for example, in the manufacturing of pantyhose articles, according to which two stockings fitted on a pair of superimposed coupled shapes must be first positioned with the respective elastic hems vertically aligned so as to have a correspondence between said elastic hems and the garter lines of the two stockings; afterwards, the stockings are cut longitudinally by starting from the elastic hem of the bodice, up to a predetermined distance from the garter line and, finally, they are sewn together along the thus cut edges. It goes without saying that in order to make the said cut with the necessary accuracy, it is necessary that the two stockings be properly positioned on the respective shapes, so as to provide a precise correspondence between the elastic hems and the garter lines and not to incur the serious drawback of making the seam with two stockings in offset relationship to each other and, thereby, manufacturing a pantyhose article with no wearability.
Also known from the Italian patent application FI92A67 of the same owner is an apparatus for automatically positioning two stockings in a machine for making pantyhose articles, in which the corresponding support shapes are extended in correspondence of the respective tips through an arc, that is a small bow of nylon thread and whose stems are moved along the shapes between two positions, one of maximum retreat, that is backwards movement, allowing the stocking to be fitted on the shapes, and the other of maximum extraction, that is drawing out movement, allowing both the bodice and the garter line resulting external to the shapes to be stretched, so as to allow the garter line to be sensed by corresponding optical sensors.
However, this known apparatus is unable to fully solve the problem relative to all types of tubular articles since it is intended to operate only on articles provided with a region of demarcation between two fabrics having different consistency, such as the garter line of a stocking, which separates the leg fabric and the bodice fabric.
It is further known from the Japanese document 1-312.410 an apparatus comprising:
optical sensors which detect the presence of two stockings on the respective shapes and are associated to corresponding first means for slidingly fitting the stockings on the shapes; PA1 optical sensors, for detecting the garter line of the thus positioned stockings, and which are associated to corresponding means for transferring the portions of stockings with garter line to a predetermined position on the shapes; PA1 optical sensors which detect the elastic hem of the stockings and are associated to corresponding second means for slidingly fitting the stockings on the shapes up to a predetermined final position. PA1 with the shapes being open, that is spaced apart, pushing each stocking, individually, towards the tip of the respective shapes, by acting, through push means, upon the horizontal upper edge of the elastic hem of the overlying stocking and, respectively, upon the horizontal lower edge of the elastic hem of the underlying stocking, along a direction parallel to the longitudinal axis of the shapes and at least up to a position of vertical alignment of the released edges, which position is determined, for each stocking, by optical detection means associated to said push means; PA1 interrupting the advancement of said push means just beyond the position of completion of detection of the inner side of the last-to-intercept elastic hem; PA1 reversing the motion of the push means and, upon interruption of the optical contact with the inner side of each elastic hem, compressing and holding the corresponding stocking at a position close to its elastic hem to allow it to be drawn towards the end of the shapes opposite to the tips, up to a predetermined point thereon; PA1 closing the shapes, that is moving them together, so as to prevent the elastic return of the stockings to a position of misalignment of the respective elastic hems; PA1 Advantageously, upon completion of the step of drawing the stocking onto the shapes, provision is made for slightly pushing the stockings towards the tip of the shapes to remove the elastic deformation of the stockings hems due to the friction taking place between the side portion of the stockings and the corresponding part of the shapes. PA1 means for detecting the presence of the free end of the article fitted on the respective flat support shapes by means of two vertically aligned optical sensors located juxtaposed on the side opposite to the shapes; PA1 means for individually moving the free end of the articles onto the respective support shapes by means of a plurality of corresponding pushers parallel to the relevant optical sensor; PA1 means for compressing a portion of each article on the relevant shape in correspondence of the free end thereof by means of two corresponding vertically aligned operating cylinders juxtaposed and located on opposite sides with respect to the shapes; PA1 means for alternately moving the sensors, the pushers and the operating cylinders, in either directions longitudinally to the shapes, by means of a carriage alternately movable in the said directions starting from the end of the shapes opposite to the tip thereof.
This known apparatus provides, after placing the two stockings on the two paired shapes, for sensing the presence thereof, operating the activation of the first means for slidingly fitting the stockings deeply on the shapes and allowing the garter lines thereof to be intercepted by the relevant sensors. Thereafter, the same first stockings-sliding means provide for the alignment of the two garter lines. Finally, the sensors for the detection of the elastic hem of the two stockings place themselves in correspondence of the position of final alignment and the said second sliding means transfer the elastic hem of the two stockings up to the corresponding position for the final alignment thereof upon the shapes.
However, also this known apparatus makes it possible to operate only on articles provided with such a neat and well visible line of demarcation between two adjacent fabric regions having different consistency as a stocking's garter line.